Method of forming trench isolation in the fabrication of integrated circuitry

ABSTRACT

This invention includes methods of forming a phosphorus doped silicon dioxide comprising layers, and methods of forming trench isolation in the fabrication of integrated circuitry. In one implementation, a method of forming a phosphorus doped silicon dioxide comprising layer includes positioning a substrate within a deposition chamber. First and second vapor phase reactants are introduced in alternate and temporally separated pulses to the substrate within the chamber in a plurality of deposition cycles under conditions effective to deposit a phosphorus doped silicon dioxide comprising layer on the substrate. One of the first and second vapor phase reactants is PO(OR) 3  where R is hydrocarbyl, and an other of the first and second vapor phase reactants is Si(OR) 3 OH where R is hydrocarbyl.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. patentapplication Ser. No. 10/615,051, filed Jul. 7, 2003, now U.S. Pat. No.7,125,815 entitled “Methods of Forming a Phosphorus Doped SiliconDioxide Comprising Layers”, naming Brian A. Vaartstra as inventor, thedisclosure of which is incorporated by reference.

TECHNICAL FIELD

This invention relates to methods of forming phosphorus doped silicondioxide comprising layers, and to methods of forming trench isolation inthe fabrication of integrated circuitry.

BACKGROUND OF THE INVENTION

One commonly used material in the fabrication of integrated circuitry issilicon dioxide. Such might be utilized as essentially 100% pure, or incombination with other materials, including property-modifying dopants.Accordingly, silicon dioxide might be utilized as a mixture with othermaterials in forming a layer or layers and may or may not constitute amajority of the given layer. Exemplary materials are borophosphosilicateglass (BPSG), phosphosilicate glass (PSG), and borosilicate glass (BSG).Typically, such materials have anywhere from 1% to 4% atomicconcentration of each of boron and/or phosphorus atoms, although atomicpercent concentrations in excess of 5% have also been used.

As semiconductor devices continue to shrink geometrically, such has hada tendency to result in greater shrinkage in the horizontal dimensionthan in the vertical dimension. In some instances, the verticaldimension increases. Regardless, increased aspect ratios (height towidth) of the devices result, making it increasingly important todevelop processes that enable dielectric and other materials to fillhigh aspect or increasing aspect ratio trenches, vias and other steps orstructures. A typical dielectric material of choice has been dopedand/or undoped silicon dioxide comprising materials, for example thosedescribed above. Dopants such as boron and phosphorus can facilitate areflowing of the deposited layer at a higher temperature to facilitatemore completely filling openings on a substrate. Various reactantprecursors can be utilized in forming silicon dioxide layers, forexample the silanols disclosed in U.S. Pat. No. 6,300,219.

SUMMARY OF THE INVENTION

This invention includes methods of forming phosphorus doped silicondioxide comprising layers, and methods of forming trench isolation inthe fabrication of integrated circuitry. In one implementation, a methodof forming a phosphorus doped silicon dioxide comprising layer includespositioning a substrate within a deposition chamber. First and secondvapor phase reactants are introduced in alternate and temporallyseparated pulses to the substrate within the chamber in a plurality ofdeposition cycles under conditions effective to deposit a phosphorusdoped silicon dioxide comprising layer on the substrate. One of thefirst and second vapor phase reactants is PO(OR)₃ where R ishydrocarbyl, and an other of the first and second vapor phase reactantsis Si(OR)₃OH where R is hydrocarbyl.

In one implementation, a method of forming a phosphorus doped silicondioxide comprising layer includes positioning a substrate within adeposition chamber. A first species is chemisorbed to a surface of thesubstrate to form a first species monolayer onto the surface within thechamber from a first vapor phase reactant comprising PO(OR)₃, where R ishydrocarbyl. The chemisorbed first species is contacted with a secondvapor phase reactant comprising Si(OR)₃OH, where R is hydrocarbyl, toform a monolayer comprising Si and O. Chemisorbing with the firstspecies and contacting the chemisorbed first species with the secondreactant are successively repeated under conditions effective to deposita phosphorus doped silicon dioxide comprising layer on the substrate.

Other aspects and implementations are contemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic sectional view of a semiconductor waferfragment in process in accordance with an aspect of the invention.

FIG. 2 is a view of the FIG. 1 wafer fragment at a processing stepsubsequent to that shown by FIG. 1.

FIG. 3 is a view of the FIG. 2 wafer fragment at a processing stepsubsequent to that shown by FIG. 2.

FIG. 4 is a diagrammatic sectional view of a semiconductor waferfragment in process in accordance with an aspect of the invention.

FIG. 5 is a view of the FIG. 4 wafer fragment at a processing stepsubsequent to that shown by FIG. 4.

FIG. 6 is a view of the FIG. 5 wafer fragment at a processing stepsubsequent to that shown by FIG. 5.

FIG. 7 is a view of the FIG. 6 wafer fragment at a processing stepsubsequent to that shown by FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

In one implementation, a method of forming a phosphorus doped silicondioxide comprising layer includes positioning a substrate to bedeposited upon within a deposition chamber. First and second vapor phasereactants are introduced in alternate and temporally separated pulses tothe substrate within the chamber in a plurality of deposition cyclesunder conditions effective to deposit a phosphorus doped silicon dioxidecomprising layer on the substrate. One of the first and second vaporphase reactants is PO(OR)₃, where R is hydrocarbyl. An other of thefirst and second vapor phase reactants is Si(OR)₃OH, where R ishydrocarbyl. Such might be conducted by atomic layer deposition (ALD)methods (for example including chemisorbing and contacting methods), bychemical vapor deposition (CVD) methods, and by other methods, as wellas by combinations of these and other methods. CVD and ALD are usedherein as referred to in the co-pending U.S. patent application Ser. No.10/133,947, filed on Apr. 25, 2002, entitled “Atomic Layer DepositionMethods and Chemical Vapor Deposition Methods”, and listing Brian A.Vaartstra as the inventor, which is now U.S. Publication No.2003-0200917. This U.S. Publication No. 2003-0200917, filed on Apr. 25,2002 is hereby fully incorporated by reference as if presented in itsentirety herein. Preferred and understood reduction-to-practice examplesprovided herein are understood to be primarily by atomic layerdeposition.

The R hydrocarbyl of the PO(OR)₃ and the R hydrocarbyl of the Si(OR)₃OHmay be the same or different, and regardless in one preferred embodimentthe R hydrocarbyl of each contains only from one to five carbon atoms.One preferred and reduction-to-practice PO(OR)₃ material comprisestriethyl phosphate. One preferred exemplary and reduction-to-practiceSi(OR)₃OH material comprises tristertbutylsilanol. Exemplary preferredconditions comprise a temperature of from about 50° C. to about 500° C.,and more preferably at from about 100° C. to about 300° C. Exemplarypressure conditions are subatmospheric, preferably being from about 10⁻⁷Torr to about 10 Torr, and more preferably from about 10⁻⁴ Torr to about1 Torr. The conditions might comprise plasma generation of at least oneof the first and second reactants, or be void of plasma generation ofthe first and second reactants. If plasma generation is utilized, suchmight occur within the chamber of deposition, and/or externally thereof.Most preferred are believed to be conditions which are void of plasmageneration of the first and second reactants.

The conditions might be effective to form the silicon dioxide comprisinglayer to have very low phosphorus content, for example to have no morethan 0.5 atomic percent phosphorus, including lesser amounts.Alternately, the conditions might be effective to form the silicondioxide comprising layer to have at least 1.0 atomic percent phosphorusincluding, for example, 5.0 and greater atomic percent phosphorus.

The method might be void of introducing any vapor phase reactant to thechamber other than the first and second vapor phase reactants in theforming of the phosphorus doped silicon dioxide comprising layer.Alternately, the method might include introducing another vapor phasereactant, different from the first and second vapor phase reactants,intermediate at least some of the separated pulses of the first andsecond vapor phase reactants. By way of example only, an exemplaryanother vapor phase reactant is oxygen containing, for example O₂, O₃and/or any vapor phase oxygen containing compound. Ozone pulses, forexample as a mixture of O₂ and O₃, in addition to the PO(OR)₃ flows havebeen determined to facilitate greater phosphorus incorporation, forexample above 5 atomic percent, if such is desired.

Another exemplary vapor phase reactant would be boron containing, andwhereby the phosphorus doped silicon dioxide comprising layer would alsothen comprise boron, for example in fabricating a BPSG or BPSG-likematerial. An exemplary boron containing material reactant is B(OR)₃.

The alternate and temporally separated pulses might include one or acombination of chamber pump down and/or purging of the chamber with aninert gas (i.e., N₂ and/or any noble gas) intermediate the separatedpulses to remove unreacted precursor/reactant.

One prior art technique of forming a silicon dioxide comprising layer isdescribed in Hausmann et al., Rapid Vapor Deposition of Highly ConformalSilica Nanolaminates, SCIENCE MAGAZINE, Vol. 298, pp. 402–406 (2002).Such a process initially utilizes a methylaluminum reactant precursor,for example triethyl aluminum or aluminum dimethylamide, which forms aninitial aluminum containing layer on the substrate. An alkoxysilanol,for example tris(tert-butoxy)silanol, is thereafter flowed to thesubstrate. Apparently, the aluminum presence provides a self-limitedcatalytic reaction whereby a silicon dioxide comprising layer depositsto some self-limiting thickness anywhere from 100 Angstroms to 700Angstroms. In other words, continued exposure to the alkoxysilanol doesnot result in continuing growth of the silicon dioxide comprising layer.Apparently, the silicon dioxide layer self-limited growth occurs in somecatalytic manner, as opposed to a simple ALD-like manner due tosignificantly more than a few monolayers being formed by the silanolexposure/pulsing. Regardless, aluminum is incorporated in the resultantlayer, which may not be desired.

While the invention disclosed herein does not preclude its use with theHausmann et al.-like process, most preferably the inventive process isvoid of introducing any vapor phase aluminum containing reactant to thechamber in the forming of the phosphorus doped silicon dioxidecomprising layer. Further preferably in accordance with the invention,the substrate is void of aluminum in the forming of the phosphorus dopedsilicon dioxide comprising layer.

In one implementation, a method of forming a phosphorus doped silicondioxide comprising layer includes at least some ALD processing. By wayof example only, an exemplary such process is described with referenceto FIGS. 1–3. Referring to FIG. 1, a substrate 10 is positioned withinany suitable deposition chamber (not shown). In one exemplaryembodiment, substrate 10 is a semiconductor substrate, for examplecomprising some material 12 which preferably includes at least somesemiconductive material, and may, of course, include multiple materialsand layers. In the context of this document, the term “semiconductorsubstrate” or “semiconductive substrate” is defined to mean anyconstruction comprising semiconductive material, including, but notlimited to, bulk semiconductive materials such as a semiconductive wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure, including, but not limited to, the semiconductive substratesdescribed above. Substrate 10 has a surface 14 which is provided to behydroxylated (having pending OH groups) as shown. Other surfacetermination is also contemplated to be effective in the process hereindescribed. If hydroxylated, such surface might by hydroxylated prior toprovision within the deposition chamber, or hydroxylated within thedeposition chamber. An exemplary technique for hydroxylating surface 14includes exposure of the surface to water vapor. Further, the surfacemight be naturally hydroxylated simply from exposure to ambientatmosphere.

Referring to FIG. 2, a first species is chemisorbed to form a firstspecies monolayer 16 onto the hydroxylated surface within the chamberfrom a first vapor phase reactant comprising PO(OR)₃, where R ishydrocarbyl, for example as described above. Such is depicted as beingcomprised of a variable “A” as constituting at least a part of layer 16in FIG. 2. Preferred conditions and other attributes are as describedabove with respect to the first described implementation.

Referring to FIG. 3, the chemisorbed first species has been contactedwith a second vapor phase reactant comprising Si(OR)₃OH, where R ishydrocarbyl, to form a monolayer 18 which will comprise Si and O. Again,conditions are preferably as described above with respect to the firstimplementation. FIG. 3 depicts layer 18 as comprising a variable “B”,with the chemisorbed first species monolayer being depicted as A′exemplary of some modification of the A species in the chemisorbing of Bwith A, with the exact preferred and typical species A and B not havingbeen determined. Regardless, chemisorbing with the first species andcontacting the chemisorbed first species with the second reactant issuccessively repeated under conditions effective to deposit a phosphorusdoped silicon dioxide comprising layer on the substrate. Typically andpreferably, such chemisorbings and contactings are conducted inalternate and temporally separated pulses to the substrate, for exampleas described above in the first described implementation.

The immediately above-described implementation was relative to thechemisorbing of a surface with PO(OR)₃ followed by a second vapor phasereactant exposure comprising Si(OR)₃OH, and by which an aspect of theinvention was reduced-to-practice, although aspects of the invention arenot necessarily so limited.

Regardless, aspects of the invention might preferably be utilized inmethods of forming trench isolation in the fabrication of integratedcircuitry, for example as shown and described with reference to FIGS.4–7. FIG. 4 shows a semiconductor substrate 26 comprising a bulkmonocrystalline silicon or other semiconductive material substrate 28. Amasking layer 30 is formed over semiconductor substrate 28. Such isdepicted as comprising a pad oxide layer 32 and an overlying nitridecomprising layer 34, for example silicon nitride.

Referring to FIG. 5, isolation trenches 36 and 38 have been etchedthrough masking layer 30 into the semiconductive material of substrate28/26. A thermal oxide layer or other layer, for example silicon nitride(not shown), might be provided now or subsequently, for example withrespect to silicon dioxide by exposing substrate 26 to thermal oxidizingconditions.

Referring to FIG. 6, a phosphorus doped silicon dioxide comprising layer40 has been formed within semiconductive material isolation trenches 36and 38. Exemplary techniques for doing so include introducing first andsecond vapor phase reactants in alternate and temporally separatedpulses to the substrate within the chamber in a plurality of depositioncycles, as described above, and also for example, by the chemisorbingsand contacting methods as described above. As depicted, the depositingis effective to deposit phosphorus doped silicon dioxide comprisinglayer 40 onto masking layer 30, and also is depicted as not beingeffective to selectively deposit phosphorus doped silicon dioxide layer40 within isolation trenches 36 and 38. In the context of this document,a “selective/selectively deposit” is one which deposits a material overone region of a substrate as compared to another at a depositionthickness ratio of at least 2:1.

The depositing might be effective to completely fill isolation trenches36 and 38, or to not fill such isolation trenches for example as shownin FIG. 6. Deposition processing, for example as described in any of theabove, could continue to completely fill such trenches, for example asshown in FIG. 7. Alternately by way of example only, the FIG. 6construction could be filled with another material before or afterremoving the material from over masking layer 30.

An exemplary reduction-to-practice example utilized triethyl phosphateand tris(tert-butoxy)silanol as first and second respective vapor phasereactants. A 650 Angstrom conformal layer of PSG (8 atomic percentphosphorus) was deposited over a silicon nitride lined trench usingrespective two second reactive pulses of each reactant, with a onesecond argon purge followed by a three second pump down without flowingargon between the reactant pulses. This was conducted for 600 completecycles at 300° C. No ozone was utilized. Respective bubbler/ampouletemperatures for feeding the triethyl phosphate andtris(tert-butoxy)silanol were 50° C. and 40° C.

Such processing was also conducted with the triethyl phosphate having atemperature of 60° C. and with tris(tert-butoxy)silanol at 70° C. One(1) second and 0.5 second respective pulses of such triethyl phosphateand of the tris(tert-butoxy)silanol yielded a 650 Angstrom film after300 complete cycles, providing an approximate 2.2 Angstrom per cyclerate of deposition. This was somewhat higher than the firstreduction-to-practice example deposition, which was at 1.1 Angstroms percycle. The deposited film was substantially carbon-free, and thephosphorus content was below 0.5 atomic percent. Longer triethylphosphate exposure at such reactant temperature is expected to yieldhigher growth rates and increase phosphorus content in the depositedfilm.

In another reduction-to-practice example, triethyl phosphate from a 60°C. bubbler/ampoule was fed to a substrate within a deposition chamberfor one second. This was followed by the flow of 30 sccm Ar for onesecond, followed by three seconds of pumping down the chamber withoutflowing any gas thereto. Thereafter, 25 sccm of a combined stream ofO₂/O₃ (5% to 12% O₃ by volume) was flowed to the chamber for twoseconds. This was followed by a 30 sccm flow of Ar for one second,followed by three seconds of pump down while feeding no gas to thechamber. Then, tris(tert-butoxy)silanol was flowed to the chamber from a60° C. bubbler/ampoule for two seconds. This was followed by one secondof Ar flow at 30 sccm, again followed by three seconds of pump downwhile no gas flowed to the chamber. This was conducted for 400 completecycles, with pressure during all of the processing varying from 0.24Torr to 10⁻⁶ Torr. Such resulted in a 1000 Angstrom thick layer having5.7 atomic percent phosphorus incorporated therein.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method of forming trench isolation in the fabrication of integratedcircuitry, comprising: forming a masking layer over a semiconductorsubstrate; etching isolation trenches through the masking layer intosemiconductive material of the semiconductor substrate; and afteretching the isolation trenches, introducing first and second vapor phasereactants in alternate and temporally separated pulses to the substratewithin the chamber in a plurality of deposition cycles effective todeposit a phosphorus doped silicon dioxide-comprising layer within theisolation trenches, one of the first and second vapor phase reactantsbeing PO(OR)₃ where R is hydrocarbyl, and an other of the first andsecond vapor phase reactants being Si(OR)₃OH where R is hydrocarbyl. 2.The method of claim 1 wherein the deposit is effective to fill theisoiation trenches.
 3. The method of claim 1 wherein the deposit doesnot fill the isolation trenches.
 4. The method of claim 1 wherein thedeposition cycles are effective to deposit the phosphorus doped silicondioxide-comprising layer on the masking layer.
 5. The method of claim 1wherein the deposition cycles are not effective to selectively depositthe phosphorus doped silicon dioxide-comprising layer within theisolation trenches.
 6. The method of claim 1 wherein the depositioncycles are effective to form the silicon dioxide-comprising layer tohave no more than 0.5 atomic percent phosphorus.
 7. The method of claim1 wherein the deposition cycles are effective to form the silicondioxide-comprising layer to have at least 1.0 atomic percent phosphorus.8. The method of claim 1 being void of introducing any vapor phasereactant to the chamber other than said first and second vapor phasereactants in said forming of the phosphorus doped silicondioxide-comprising layer.
 9. The method of claim 1 comprisingintroducing another vapor phase reactant different from the first andsecond vapor phase reactants intermediate at least some of saidseparated pulses of the first and second vapor phase reactants.
 10. Themethod of claim 9 wherein the another vapor phase reactant isoxygen-containing.
 11. The method of claim 10 wherein the another vaporphase reactant comprises O₃.
 12. The method of claim 9 wherein theanother vapor phase reactant is boron-containing, the phosphorus dopedsilicon dioxide-comprising layer comprising boron.
 13. The method ofclaim 1 wherein the PO(OR)₃ comprises triethyl phosphate.
 14. The methodof claim 1 wherein the Si(OR)₃OH comprises tris(tert-butoxy)silanol. 15.The method of claim 1 wherein the PO(OR)₃ comprises triethyl phosphateand wherein the Si(OR)₃OH comprises tris(tert-butoxy)silanol.
 16. Themethod of claim 1 comprising purging the chamber with an inert gasintermediate the separated pulses.
 17. The method of claim 1 being voidof aluminum on the substrate in said forming of the phosphorus dopedsilicon dioxide-comprising layer.
 18. The method of claim 1 being voidof introducing any vapor phase aluminum-containing reactant to thechamber in said forming of the phosphorus doped silicondioxide-comprising layer.
 19. The method of claim 1 wherein thedeposition cycles comprise atomic layer deposition.
 20. The method ofclaim 1 wherein the deposition cycles comprise plasma generation of atleast one of the first and second reactants.
 21. The method of claim 1wherein the deposition cycles are void of plasma generation of the firstand second reactants.